refactor: define prompts in configuration

config_sentence_transformers.json

@@ -4,7 +4,10 @@
     "transformers": "4.41.2",
     "pytorch": "2.3.1+cu121"
   },
-  "prompts": {},
+  "prompts": {
+    "retrieval.query": "Represent the query for retrieving evidence documents: ",
+    "retrieval.passage": "Represent the document for retrieval: ",
+  },
   "default_prompt_name": null,
   "similarity_fn_name": "cosine"
 }